In a system that a computer of a user (user computer), a computer of a service provider (center computer) and a computer of a software vender (software vendor) are capable of communicating with each other, conventional technology for updating software of the user computer is, for example, that the center computer has a data base necessary for updating software installed in the user computer and the user installs data such as a part of the database. Then the user judges which of the update software to be obtained by exchanging data with the center computer. Having determined the software to be installed, the user receives information on URL (Uniform Resource Locator) of the software vendor from the center computer and using the information on URL, the user installs update software from a computer (site) of the software vendor.    [Patent Literature 1] Japanese laid-open patent application publication 10-91407 (paragraph [0027], [0028], [0029], [0030], [0031], [0032], [0033], [0034] and [0035], FIG. 2 and so on.